When Gloom Blooms in June, Is Catalina Eddy the Reason for the Season?

The elusive swirl of breezes called the Catalina Eddy, responsible for helping cool the Los Angeles basin, is captured in a new animation of sea-surface winds measured by the SeaWinds instrument on NASA's QuikScat satellite. During the hot, dry summer months these gentle winds are welcomed because they direct the offshore marine layer toward the Los Angeles basin. Because the flow is more onshore than normal, this cooling oceanic influence of the eddy has been described as nature's purifier or air-conditioner for Los Angeles. The animation is online at:

Beta-SP copies of the video are available for broadcasters by calling Xaviant Ford at (818) 353-4484.

While the Catalina Eddy, an atmospheric vortex or eddy with a counter-clockwise rotation pattern, can occur in the California Bight (the open ocean bay formed by the bend in the coast between Point Conception to the north and San Diego to the south) at any time of the year, it is most often seen during May and June. It can develop when the winds from the northwest along the Southern California coast are stronger than normal and interact with the local coastal and land topography, turning inland and creating a vortex.

Only about 200 kilometers (120 miles) in diameter, the Catalina Eddy has not been well measured by scientists. The eddy is actually too small to appear in current weather forecast models and is sometimes too shallow to have a strong influence on the cloud structure viewed by weather satellites. But in this animation, the high-resolution capability of the SeaWinds instrument has visualized its complete circulation. This capability allows scientists to study these smaller-scale wind events that can have such a profound impact on local climate.

The SeaWinds on QuikScat project is managed for NASA's Earth Science Enterprise by NASA's Jet Propulsion Laboratory, Pasadena, Calif. More information about SeaWinds is available online at http://winds.jpl.nasa.gov/missions/quikscat/.

JPL is a division of the California Institute of Technology in Pasadena.